The present invention relates to a simple process for metallizing substrates by effective activation of the substrate by deposition of palladium from a palladium compound, followed by electroless metallization of the activated substrate in a metallizing bath.
As disclosed, e.g., in the monograph by F. A. Loewenheim, Metal Coating of Plastics, Noyes Data Corp., Park Ridge, N.J., 1970, the pretreatment of substrates for electroless metallization is usually very time-consuming. After a chemical pretreatment, e.g. with chromosulfuric acid, or a mechanical pretreatment of the substrate surfaces, the conventional activation entails sensitizing the substrate with tin salts, rinsing it and then applying palladium chloride to activate the substrate.
U.S. Pat. No. 3,501,332 discloses the activation of plastics with zero-valent metal complexes, e.g. bis-(cyclooctadienyl)-nickel in organic solvents. In this method, the combination of metal complex and organic solvent is intended to swell the surface of the substrate so as to permit the metal complex to penetrate to a depth of at least 5 .mu. and preferably to a depth of from 5 to 80 .mu.. Substrates whose surface is difficult to swell must be subjected to a special pretreatment.